The invention relates to a control method for diagnosing an exhaust pressure regulator.
Present regulatory conditions in the automotive market have led to an increasing demand to improve fuel economy and reduce emissions in present vehicles. These regulatory conditions must be balanced with the demands of a consumer for high performance and quick response for a vehicle.
An exhaust gas pressure regulator is used in many types of engines to create a back pressure in the exhaust gas system, for example in order to improve the braking force of a four-stroke or two stroke internal combustion engine. In addition, the back pressure from an exhaust gas pressure regulator can be utilized to increase the amount of re-circulated gas to the intake side, so called EGR-gas. In addition, the back pressure can be utilized for heating up the engine more quickly when starting. An exhaust gas pressure regulator is normally located downstream of a turbo charging system in order not to have an adverse effect on the efficiency.
An exhaust gas pressure regulator, for instance a butterfly flap, may work together with a pressure sensor situated between a turbine of a turbo and said butterfly flap. The problem today is that it is not possible to determine whether it is the flap or the pressure sensor that is the source of an eventual failure. E.g., if the pressure sensor displays a faulty low pressure, then the system wants to close the butterfly flap even more, which may result in severe engine damages.
It is desirable to provide an improved diagnosis method of an exhaust gas pressure regulator.
In a first aspect of the present invention it is provided a diagnostic method for an exhaust pressure regulator provided in an exhaust system connected to a turbocharged internal combustion engine, comprising the steps of: demanding engine brake, measuring a back pressure in the exhaust system by a back pressure sensor when demanding engine brake, measuring the boost pressure by a boost pressure sensor when demanding engine brake, comparing the measured back pressure and the measured boost pressure with stored back pressure and boost pressure values in order to determine whether there is a defective pressure regulator or a defective backpressure sensor.
An advantage of this embodiment of the present invention is that it will yield in safer and more precise diagnostics.
Another advantage of the present invention is that it will be easier to trace faults in the system.
Still another advantage of the present invention is that it also will minimize the risk of engine damage due to failure on the system.
In another embodiment of the present invention it further comprising the step of alarming an operator if there is a defective pressure regulator or back pressure sensor.
An advantage of this embodiment is that the fault not only can be traced during servicing the vehicle but also actively alarming the driver of the vehicle that something is wrong. The driver may take own decisions on what to do, for instance shutting off the engine. The decision of shutting off the engine may also be automatically performed depending on the severity of the problem.
In still another embodiment of the present invention said backpressure sensor is defective if the measured backpressure is below a predetermined value and the measured boost pressure is below a predetermined value.
In still another example embodiment of the present invention said pressure regulator is defective if the measured backpressure is below a predetermined value and the measured boost pressure is above a predetermined value.
In yet another embodiment of the present invention said backpressure sensor is defective if the measured backpressure is above a predetermined value and the measured boost pressure is above a predetermined value.
In yet another example embodiment of the present invention said pressure regulator is defective if the measured backpressure is above a predetermined value and the measured boost pressure is below a predetermined value.
The advantages of the above mentioned example embodiments are that different failure reasons may be separated by comparing detected back pressure and boost pressure.
In another aspect of the present invention it is provided a diagnostic apparatus for an exhaust pressure regulator provided in an exhaust system connected to a turbocharged internal combustion engine, comprising: means for demanding engine brake, means for measuring a back pressure in the exhaust system by a back pressure sensor when demanding engine brake, means for measuring the boost pressure by a boost pressure sensor when demanding engine brake, means for comparing the measured back pressure and the measured boost pressure with stored back pressure and boost pressure values in order to determine whether there is a defective pressure regulator or a defective backpressure sensor.
In the drawings, equal or similar elements are referred to by equal reference numerals. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. Moreover, the drawings are intended to depict only typical embodiments of the invention and therefore should not be considered as limiting the scope of the invention.